Abstract: Vegetation and soil coupling characteristics of Haloxylon ammodendron plantation during the process of sand-fixation was studied, in order to promote the interaction between vegetation and soil and provide a scientific basis to optimize the restoration of vegetation in arid sandy areas. Based on the comprehensive investigation and sampling analysis of vegetation and soil system of 7-42 years H. ammodendron plantations in the southern of the Gurbantunggut desert, two index systems with eleven vegetation factors and seven soil factors were set up. Analytic hierarchy process was used to determine the weight of each factor and construct models on vegetation-soil coupling and coupling coordination degree of nine different aged plantations. Then the method of principal component analysis was used to make variable dimension reduction and comprehensive evaluation. The results showed that, vegetation and soil system coupling degree and coupling coordinative degree of H. ammodendron plantations in different sand fixation years were not one-to-one correspondence. Positions of the comprehensive index of vegetation (f_x) and soil (f_y) were not completely consistent in different aged plantations. The system of H. ammodendron plantations always stayed in disorder recession, vegetation and soil were proned to loss type during the process of sand-fixation. Five principal components evaluated that the first rank was 42 years plantation. The vegetation and soil system was inferred that had the trend from senescence to harmoniousdevelopment.So the trend of coordinated development between vegetation and soil would be promoted, if the artificial tending and management measures strengthened.

Key words: Haloxylon ammodendron plantation, vegetation and soil coupling degree, coupling coordinative degree